I will admit to being guilty of this too with role-playing games even ones whose theme - background is the reason I play them at all. I feel however that with both if the theme is integrated into the game & the mechanics reflect & re emphasise it continually then its much easier to appreciate it. I would also plead in my defence that I mostly do this sort of thing to get on and play the game as lengthy rules expositions tend to affect me in the same way as Vogon poetry.....
Ginger